The present invention relates to vacuum cleaners, particularly upright style vacuum cleaners and, more particularly, to a counter-balance mechanism for compensating for the weight of the handle and main body of the vacuum cleaner when it is tilted relative to the cleaning head of the vacuum cleaner.
It is well known in the prior art to provide a counter-balance mechanism for the handle and main body portion of an upright vacuum cleaner to reduce the weight supported by the operator when the handle and main body of the vacuum cleaner is moved from its upright position to a more horizontal position. Such counter-balance mechanisms generally use a torsion spring. The counter-balance mechanism is generally positioned between the main body and cleaning head of the vacuum cleaner so that as the handle is moved from an upright position to a more horizontal position the counter-balance mechanism increases the counter force supplied by the torsion spring so that more of the weight is carried by the cleaning head rather than the operator through the handle. Such counter-balance mechanisms hold the torsion coils in a fixed location so that the coiling and uncoiling occur around a fixed central axis utilizing a central shaft or an outer cylinder encasing the torsion coils, many in such a manner that the coils of the torsion spring engage the shaft or cylinder causing substantial wear over time and interfering with the effective rate of the spring so as to either lesson the counter force or increase it. Some of these prior art devices, such as U.S. Pat. Nos. 2,291,250 and 2,684, 271, teach the use of torsion springs in which one or both of the ends of the spring are free to move in a straight line over an engaging surface as the main body is pivoted relative to the cleaning head. This later design, in particular, promotes substantial wear as the spring end moves over the mating surface, eventually leading to breakage.